Video compression addresses the problem of reducing the amount of data required to represent video and a number of standards have been available for implementation. The video coding standards in use today can be grouped into two broad categories according to their intended applications: (i) video teleconferencing standards such as H.261 and H.264 which have been defined by the International Telecommunications Union (ITU) and (ii) multimedia standards such as MPEG-2, MPEG-4 which are developed under the auspices of the Motion Picture Experts Group of the CCITT and ISO.
Despite the existence of a variety of video coding standards, most rely on similar video compression techniques. These techniques include the still image compression techniques due to the fact that video is made up of a series of still images known as frames (or fields). For example, predictive coding techniques such as DPCM (Differential Pulse Code Modulation) which is a spatial domain method, and DCT (Discrete Cosine Transform) which is a transform coding making use of a reversible, linear transform to map the image into a set of transform coefficients. The coefficients are then quantized and coded.
Besides reducing the spatial redundancy, these video compression techniques also make use of motion estimation and motion compensation in order to reduce temporal redundancies. Moving objects in video often appear from frame (or field, both terms can be used interchangeably for simplicity hereinafter) to frame with all or part of it relocated in those subsequent frames. Despite those relocations, correlation among the sequence of frames is high and gives rise to redundancy. This so-called temporal redundancy can be reduced by comparing and relating the pixel in the present frame to the location of the same object in the preceding reference frame.
For example, the PCT international patent application with publication number WO 2006/108654 A2 published on 19 Oct. 2006 in the name of Universität Hannover describes “Method and Apparatus for Enhanced Video Coding”; the U.S. patent application with publication number US 2003/0169931 A1 published on 11 Sep. 2003 in the name of Jani Lainema describes “Coding Dynamic Filters”; the U.S. patent application with publication number US 2004/0076333 A1 published on 22 Apr. 2004 in the name of Huipin Zhang and Frank Bossen describes “Adaptive Interpolation Filter System for Motion Compensated Predictive Video Coding”; the PCT international patent application with publication number WO 2007/009875 A2 published on 25 Jan. 2007 in the name of Thomson Licensing describes “Method and Apparatus for Encoding Video Data, and Video Signal Obtained from said Method or Apparatus”; and the U.S. patent application with publication number US 2006/0294171 A1 published on 28 Dec. 2006 in the name of Frank Bossen and Alexandros Tourapis describes “Method and Apparatus for Video Coding and Decoding using Adaptive Interpolation”.